Bought a reman trans and new clutch for my 91 Nissan pickup it runs good besides in 4th gear and cruising down while in 4th gear it will pop out of gear around 45 mph
Hi there - it is possible that your "popping out of gear" problem is worn shifter linkage, bad transmission or shifter mount, or worn shift detents in the shift selector shafts. These are (relatively) easily checked without dropping the transmission. Otherwise, a worn synchronizer sleeve, shift fork, or synchronizer (as you suspect) are the most common causes of this problem. I would recommend a transmission shifting inspection by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.
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